The present invention relates to laser enhanced transluminal angioplasty catheters and particularly to apparatus in such catheters for inserting an optical fiber into the catheter, and for controlling the times at which laser energy is introduced into the fiber.
Angioplasty catheter devices have been found useful in treating occlusions formed in blood vessels, for example, from plaque build-up. In a laser enhanced catheter, an optical fiber is used to transmit a beam of laser energy from a generator to the fiber distal end, where the laser energy is delivered to and against the obstruction. Under controlled exposure to the laser energy, the obstruction is partially removed, reduced in size, or eliminated entirely, effectively re-opening the blood vessel to restore normal circulation.
The success of this procedure, however, is largely dependent upon the skill with which the physician manipulates the catheter and optical fiber. Typically, fluoroscopy techniques, such as incorporation of radiopaque markers near the catheter distal end, assist in control of the catheter. A problem more particular to the optical fiber is the requirement that it be advanced beyond the catheter distal end by a controlled amount. To avoid damage to the fiber, it is preferably retracted within the catheter while the catheter is inserted, to be later advanced beyond the catheter tip. Care must be taken to avoid introducing laser energy into the fiber until its distal end has emerged beyond the catheter tip. Otherwise, the catheter lumen containing the fiber can be damaged.
U.S. Pat. No. 4,669,465, assigned to the assignee of the present application, discloses a laser catheter control and connecting apparatus including a zero adjust knob 60 threadedly engaged to the fiber advance manifold 14, for adjusting the position at which a Hall effect switch automatically turns off the laser source upon optical fiber retraction. While this apparatus can effectively ensure against premature transmission of laser energy through the optical fiber, it requires the exclusive attention of the physician or other operator, and its adjustment requires both hands.
It therefore is an object of the present invention to provide a conveniently adjustable apparatus for selectively enabling and disabling transmission of laser energy through an optical fiber.
Another object of the invention is to provide a zero positioning switch in a laser enhanced transluminal catheter that can be adjusted with one hand, and without demanding the exclusive attention of the physician or other user.
Yet another object of the invention is to provide a zero positioning switch mounted to a fiber advance housing, and adjustable by an operator using the same hand that is holding the fiber advance housing.